1. Technical Field
This invention relates to dragline excavating machines which have a main support center pin assembly. Dragline excavation machines are supported on a central stabilization tub during excavating. As such, stress is imparted thereto by the shear weight of the machine and the excavating movements required during use. Such large machines are movable from location to location by use of a walking mechanism that lifts the entire machine up and forward repeatedly imparting increased stress and wear to the center pin and support structure as well as during use in which lateral forces are encountered and the machine pivots on the center pin support structure.
2. Description of Prior Art
Prior art support tubs and center pin assemblies can be seen in the following U.S. Pat. Nos. 5,154,012, 5,154,013, 5,676,471.
In U.S. Pat. No. 5,154,012 a support tub for a dragline excavating machine is described with a circular tracking ring support and a lifting stool assembly with a center pin lifting pin threadably secured within a bearing support frame.
U.S. Pat. No. 5,154,013 is a support tub for a dragline directed to a lifting stool with lifting pivot pin.
U.S. Pat. No. 5,676,471 claims a dragline excavator with improved thrust bearing assemblies support upper structure. A center pin connects the upper structure to the lower structure of the support. A perimeter annular rail with rollers provide for rotation of the structure thereabout.